1. Field of the Invention
The invention relates generally to fasteners and particularly relates to nut-and-bolt connections in articles or structures subjected to shock loads or subjected to severe conditions tending to fatigue fasteners.
2. Background Art
The invention teaches a fastener assembly where a specially designed tapered nut reduces concentration of longitudinal stress on bolt threads engaged with the nut. A relevant item of prior art is an article entitled “Reduction of Stress Concentration in Bolt-Nut Fasteners” by Srinan Venkatesan and Gary L. Kinzel published in the November 2006 issue of the Journal of Mechanical Design. That article discusses various modifications to nuts and bolts to reduce stress concentration on fastener threads. The most relevant modification is Model F shown in Table 1 of the article. Model F shows a bevel on the nut in conjunction with a groove on the end of the bolt; the article dismisses the Model F construction as unworthy of further study because a Model E, which has a notch on the nut as opposed to a bevel, was more effective. An article dealing generally with longitudinal stress on fastener threads is “Notes on Nuts and Bolts” at http://www.gizmology.netinuts/bolts.htm. Tapered nuts are commonly used in a fashion wherein the outer surface of the nut bears against a complimentary tapered seat or socket as seen for, example, in FIG. 6 of U.S. Pat. No. 5,279,407 to Shoback.